forking and killing parent processes Post: 86644

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Top Forums UNIX for Dummies Questions & Answers forking and killing parent processes Post 86644 by davewilliams20 on Monday 17th of October 2005 05:40:47 AM

10-17-2005

Registered User

forking and killing parent processes

Hi everybody,

I'm having some problems wiriting a program in UNIX using the "fork" and "kill" system calls.

I have to create a C program P0, which creates 9 other processes
P1, P2, ..., P9, where P0 is the father of P1, P1 the father of P2, and so on.

All the processes contain an infinite loop.

When all the processes are created P9 executes the command "ps".
Then P9 kills P8, execute "ps", then kills P7, executes "ps", and so
on till only the process P0 and P9 remain.

I've created the 9 processes in the following way:

P0 does a fork. The child process executes p1 and the parent process enters and infinite loop.
p1 to p8 do the same thing.
p9 then executes ps.

Up to here there are no problems, ps is executed and everything seems to be working fine, the PID and PPID are correct, and all the processes are marked as running.

The problem I have is how to kill the parents of p9.

I use the kill function, but for this I need the PID of the processes to kill.
How can this be found?

To see at least if the kill process does what's it supposed to do, I use the getppid() system call to retrieve the PID of process p9's father and loop it back from there (not very elegant but should work in theory).

With this pid I then use the kill function with the SIGKILL signal and the pid of the process to be killed.

The problem here is that only p8 gets killed while the rest of the processes keep running!

Therefore the process p9 does something like this:

Code:

int main() {

	execute_ps()

	kill_parents()

}

void execute_ps() {

	pid = fork();

	if (fork != 0)
		wait();

	else
		execl("/bin/ps","",0)

}

void kill_parents() {

	parent = getppid();

	for (i=0; i<8; i++) {

		kill(parent, SIGKILL);
		parent--;
		execute_ps();

	}

	execute_ps();

}

Any help/suggestions are welcome!

Thanks a lot

David

davewilliams20

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LEARN ABOUT X11R4

kill

KILL(1)                                                            User Commands                                                           KILL(1)

NAME

       kill - send a signal to a process

SYNOPSIS

       kill [options] <pid> [...]

DESCRIPTION

       The  default  signal  for kill is TERM.  Use -l or -L to list available signals.  Particularly useful signals include HUP, INT, KILL, STOP,
       CONT, and 0.  Alternate signals may be specified in three ways: -9, -SIGKILL or -KILL.  Negative PID values may be  used  to  choose  whole
       process  groups;  see  the  PGID  column  in ps command output.  A PID of -1 is special; it indicates all processes except the kill process
       itself and init.

OPTIONS

       <pid> [...]
              Send signal to every <pid> listed.

       -<signal>
       -s <signal>
       --signal <signal>
              Specify the signal to be sent.  The signal can be specified by using name or number.  The behavior of signals is explained  in  sig-
              nal(7) manual page.

       -l, --list [signal]
              List signal names.  This option has optional argument, which will convert signal number to signal name, or other way round.

       -L, --table
              List signal names in a nice table.

       NOTES  Your shell (command line interpreter) may have a built-in kill command.  You may need to run the command described here as /bin/kill
              to solve the conflict.

EXAMPLES

       kill -9 -1
              Kill all processes you can kill.

       kill -l 11
              Translate number 11 into a signal name.

       kill -L
              List the available signal choices in a nice table.

       kill 123 543 2341 3453
              Send the default signal, SIGTERM, to all those processes.

SEE ALSO

       kill(2), killall(1), nice(1), pkill(1), renice(1), signal(7), skill(1)

STANDARDS

       This command meets appropriate standards. The -L flag is Linux-specific.

AUTHOR

       Albert Cahalan <albert@users.sf.net> wrote kill in 1999 to replace a bsdutils one that was not standards  compliant.   The  util-linux  one
       might also work correctly.

REPORTING BUGS

       Please send bug reports to <procps@freelists.org>

procps-ng                                                          October 2011                                                            KILL(1)

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